Werner Eugster

Last Name

Eugster

First Name

Werner

ORCID

0000-0001-6067-0741

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Publications1 - 10 of 226

Performance of a low-cost methane sensor for ambient concentration measurements in preliminary studies
Eugster, Werner; Kling, G. W. (2012)
Atmospheric Measurement Techniques
Methane is the second most important greenhouse gas after CO2 and contributes to global warming. Its sources are not uniformly distributed across terrestrial and aquatic ecosystems, and most of the methane flux is expected to stem from hotspots which often occupy a very small fraction of the total landscape area. Continuous time-series measurements of CH4 concentrations can help identify and locate these methane hotspots. Newer, low-cost trace gas sensors such as the Figaro TGS 2600 can detect CH4 even at ambient concentrations. Hence, in this paper we tested this sensor under real-world conditions over Toolik Lake, Alaska, to determine its suitability for preliminary studies before placing more expensive and service-intensive equipment at a given locality. A reasonably good agreement with parallel measurements made using a Los Gatos Research FMA 100 methane analyzer was found after removal of the strong sensitivities for temperature and relative humidity. Correcting for this sensitivity increased the absolute accuracy required for in-depth studies, and the reproducibility between two TGS 2600 sensors run in parallel is very good. We conclude that the relative CH4 concentrations derived from such sensors are sufficient for preliminary investigations in the search of potential methane hotspots.
A fault-tolerant eddy covariance system for measuring CH4 fluxes
Eugster, Werner; Plüss, Peter (2010)
Agricultural and Forest Meteorology
Stable water isotopologue ratios in fog and cloud droplets are not size-dependent
Spiegel, Johanna K.; Aemisegger, Franziska; Scholl, Martha; et al. (2012)
Atmospheric Chemistry and Physics
In this work, we present the first observations of stable water isotopologue ratios incloud droplets of different sizes collected simultaneously. We address the questionwhether the isotope ratio of droplets in a cloud varies as a function of droplet size. Sam-ples were collected from a ground intercepted cloud (=fog) during the Hill Cap Cloud Thuringia 2010 campaign (HCCT-2010) using a three-stage Caltech Active StrandCloud water Collector (CASCC). An instrument test revealed that no artificial isotopicfractionation occurs during sample collection with the CASCC. Furthermore, we couldexperimentally confirm the hypothesis that theδvalues of cloud droplets of the rele-vant droplet sizes (μm-range) were not significantly different and thus can be assumed to be in isotopic equilibrium immediately with the surrounding water vapor. However, atthe dissolution period of the cloud differences in isotope ratios of the different dropletsizes tended to be larger. This is likely to result from the cloud’s heterogeneity, implyingthat larger and smaller cloud droplets have been collected at different moments in time,delivering isotope ratios from different collection times.
Technical note: High accuracy weighing micro-lysimeter system for long-term measurements of non-rainfall water inputs to grasslands
Riedl, Andreas; Li, Yafei; Buchmann, Nina; et al. (2021)
Hydrology and Earth System Sciences Discussions
Non-rainfall water (NRW), defined here as dew, hoar frost, fog, rime and water vapor adsorption, might be a relevant water source for ecosystems, especially during summer drought periods. These water inputs are often not considered in ecohydrological studies, because water amounts of NRW events are rather small and therefore difficult to measure. Here we present a novel micro-lysimeter (ML) system and its application which allows to quantify very small water inputs from NRW with an unprecedented high accuracy of ±0.25 g, which corresponds to ±0.005 mm water input. This is possible with an improved ML design paired with individual ML calibrations in combination with high-frequency measurements at 3.3 Hz and an efficient low-pass filtering to reduce noise level. With a set of ancillary sensors, the ML system furthermore allows differentiating between different types of NRW inputs: dew, hoar frost, fog, rime and the combinations among these, but also additional events when condensation on leaves is less probable, such as water vapor adsorption events. In addition, our ML system design allows to minimize deviations from natural conditions in terms of canopy and soil temperatures, plant growth and soil moisture. This is found to be a crucial aspect for obtaining realistic NRW measurements in short-statured grasslands. Our ML system has proven to be useful for high-accuracy, long-term measurements of NRW on short-statured vegetation like grasslands. Measurements with the ML system at a field site in Switzerland showed that NRW input occurred frequently with 127 events over 12 months, with a total NRW input of 15.9 mm. High average monthly NRW inputs were measured during summer months, suggesting a high ecohydrological relevance of NRW inputs for temperate grasslands.
Respiration losses of the Swiss Carbo Europe cropland site
Eugster, Werner; Flechard, Christophe R.; Ammann, Christof; et al. (2006)
Geophysical Research Abstracts
Temporal and spatial variations of CO2, CH4 and N2O fluxes at three differently managed grasslands
Imer, Dennis; Merbold, Lutz; Eugster, Werner; et al. (2013)
Biogeosciences Discussions
Far-red sun-induced chlorophyll fluorescence shows ecosystem-specific relationships to gross primary production: An assessment based on observational and modeling approaches
Damm, A.; Guanter, L.; Paul-Limoges, E.; et al. (2015)
Remote Sensing of Environment
CO2 exchange of a grassland and a wetland in the Swiss Pre-Alps during the 2003 heat wave
Rogiers, N.; Furger, M.; Eugster, Werner (2006)
Geophysical Research Abstracts
Quality control of CarboEurope flux data: Part 2: Inter-comparison of eddy-covariance software
Mauder, Matthias; Foken, Thomas; Clement, Robert J.; et al. (2008)
Biogeosciences
As part of the quality assurance and quality control activities within the CarboEurope-IP network, a comparison of eddy-covariance software was conducted. For four five-day datasets, CO2 flux estimates were calculated by seven commonly used software packages to assess the uncertainty of CO2 flux estimates due to differences in post-processing. The datasets originated from different sites representing different commonly applied instrumentation and different canopy structures to cover a wide range of realistic conditions. Data preparation, coordinate rotation and the implementation of the correction for high frequency spectral losses were identified as crucial processing steps leading to significant discrepancies in the CO2 flux results. The overall comparison indicated a good although not yet perfect agreement among the different software within 5–10% difference for 30-min CO2 flux values. Conceptually different ideas about the selection and application of processing steps were a main reason for the differences in the CO2 flux estimates observed. A balance should be aspired between scientific freedom on the one hand, in order to advance methodical issues, and standardisation of procedures on the other hand, in order to obtain comparable fluxes for multi-site synthesis studies.
Climate control of terrestrial carbon exchange across biomes and continents
Yi, Chuixiang; Ricciuto, Daniel; Li, Runze; et al. (2010)
Environmental Research Letters

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Werner Eugster

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